1. Field of the Invention
The present invention relates to an image processing apparatus that reads an original placed on an original platen (or document table) of an image reading apparatus, processes an image of the read original, and cuts out and outputs only an original area placed on the platen.
2. Description of the Related Art
To read an original placed on an original platen and cut out an original area from the read image, a known technique extracts a contour surrounding the original and cuts out a rectangular part surrounded by the contour as the original area. The contour of the read image is first extracted to cut out the read original area. As an extraction method there is well-known a method of using an image processing filter often used in general image processing to search a significant change in color or luminance of a target pixel compared to surrounding pixels. In this method, a certain threshold is set to a result value obtained by using an image processing filter to easily extract the contour, and the extracted contour is used to cut out the original area of the read image.
Japanese Patent Application Laid-Open No. 2004-201240 discloses an invention for detecting RGB array patterns of the entire original platen surface and detecting a border between the backside of a scanner cover, which presses the original, and the original area, i.e. a contour of the original, based on the difference in gradations.
Japanese Patent Application Laid-Open No. H06-178086 discloses an invention for specifying connections by making a collation of the original torn and separated into a plurality of pieces of paper based on the shapes of cut sides and features of images of the cut sides to detect nonlinear cut sides.
However, the following problems exist in the method of extracting the contour of the read image when the contour of the original is nonlinear, especially when the cut sides of the original are finely cut into sawtooth shapes. More specifically, shades are formed on the nonlinear cut sides due to irregular reflection by the light of the light source illuminating the original and the reflected light of a pressure plate pressing the original. The shades are extracted as an intermittent, regular contour. Therefore, a straightly continuous contour cannot be extracted, and the contour of the original cannot be extracted. Thus, there is a problem that the original with nonlinear contour of original cannot be appropriately cut out to read the image. In the method of collating the broken lines of the torn original, there is also a problem that the features are falsely detected when the cut sides are in a finely sawtooth shape because shades are formed by the irregular reflection.
An object of the present invention is to provide an image processing apparatus that can appropriately cut out and read an original area of an original even if there are shades on nonlinear cut sides, caused by the leakage of light caused by irregular reflection of light by the light source illuminating the original and the reflected light of a pressure plate pressing the original.